Virtual reality systems present images to a user representing scenes at a location, either real or imaginary. In such a system, the user may move around the location or take actions which alter the scene. For example, in an outdoor location, the user may move down a street or path passing buildings, trees, and other objects. The scene changes as the user moves. The user may turn to face different directions which also causes the scene to change. The user may also move or pick up objects. One of the difficulties for a creator of a virtual reality system is the need to create a large number of scenes with different characteristics. Typically, this is done by specifying the objects (such as buildings, trees, vehicles, etc.) at each location.
Often virtual reality systems have multiple participants. The participants move around in the location and interact with each other. Typically, the participants have different goals, objectives, and expectations about the virtual reality location.
The design of the location must account for these differences. In order to provide greater diversity, the system creator may allow the participants to assist in generating portions of the location, with corresponding characteristics. Creation by multiple participants raises additional problems of integration and joint operation.
Lucasfilm Games created a system called "Habitat" which is a multi-user, on-line simulated world. The operations and problems with this world are discussed in C. Morningstar and F. R. Farmer, "The Lessons of Lucasfilms', Habitat" Cyberspace: First Steps (ed. M. Benedikt, 1991). In this system, online participants see views of a world with characters representing themselves and other participants acting within the world. One of the difficulties for Habitat was the creation of a world capable of supporting a population of thousands or tens of thousands of participants. The creators of Habitat tried to centrally plan and generate the entire world. With large numbers of participants, the world had to be large and to include things to do which would be of interest to the various participants. This required the design of many buildings, road networks, objects, and areas. Furthermore, in order to generate interest, the designs had to be diverse. Respective designs and architectures are uninteresting in the real world and in virtual reality. This proved to be extremely difficult for the central planner. Thus, a need exists for a system which allows the creation of a large scale virtual reality environment with diversity.
Urban planners have used systems which describe locations in general terms. The Image of the City (1960) by Kevin Lynch describes five elements that people use to organize a mental image of a city or region. "Districts" are broad regions, such as neighborhoods, which have some common identifying character. "Paths" are channels, such as roads or walkways, along which an observer can move. "Edges" are boundaries between districts. "Nodes" are specific objects to and from which an observer may travel. Finally, "landmarks" are points used for general orientation, locally or globally. While these constructs are used for understanding, describing, and designing real-world cities or other locations, they have not been used for designing places in virtual reality environment.
Therefore, a need exists for a system to allow generation of a virtual reality location by multiple participants. A need also exists for a system which provides structure to the virtual reality environment. A need also exists for a system which allows for diversity in the creation of the environment.